Photonic realization of erasure-based nonlocal measurements

TL;DR

This paper demonstrates an experimental scheme for nonlocal quantum measurements using probabilistic quantum erasure, enabling local access to nonlocal information without classical communication, with implications for quantum communication and computation.

Contribution

The work introduces a novel photonic implementation of nonlocal measurements via quantum erasure, bypassing traditional restrictions and enabling local access to nonlocal quantum information.

Findings

Successfully performed high-accuracy nonlocal measurements of parity and Bell basis.

Achieved local measurement outcomes through postselection without classical communication.

Reconstructed quantum states confirming the retrieval of nonlocal information.

Abstract

Relativity theory severely restricts the ability to perform nonlocal measurements in quantum mechanics. Studying such nonlocal schemes may thus reveal insights regarding the relations between these two fundamental theories. Therefore, for the last several decades, nonlocal measurements have stimulated considerable interest. However, the experimental implementation of nonlocal measurements imposes profound restrictions due to the fact that the interaction Hamiltonian cannot contain, in general, nonlocal observables such as the product of local observables belonging to different particles at spacelike-separated regions. In this work, we experimentally realize a scheme for nonlocal measurements with the aid of probabilistic quantum erasure. We apply this scheme to the tasks of performing high accuracy nonlocal measurements of the parity, as well as measurements in the Bell basis, which do not necessitate classical communication between the parties. Unlike other techniques, the nonlocal measurement outcomes are available locally (upon successful postselection). The state reconstructed via performing quantum tomography on the system after the nonlocal measurement indicates the success of the scheme in retrieving nonlocal information while erasing any local data previously acquired by the parties. This measurement scheme allows realizing any controlled-controlled-gate with any coupling strength. Hence our results are expected to have conceptual and practical applications to quantum communication and quantum computation.